Means for and method of reducing cross talk in four-wire circuits



, R. A. RENSHAW. MEANS FOR AND METHOD OF REDUCING. CROSS TALK IN FOURWIRE CIRCUITS.

. APPLICATION FILED JAN.2, ,320. 1-A35598Q Patented Nov, 2L 1922i,

f ATTORNEY Patented Nov. El,

BIGTIABJD A. RENSI-ZAXV, OLE 'ViTGODHr-LVEN, NEH] 1 03K, ASSIC-li-TOR330 i iLl /IEEICAN TELE PHONE AND TELEGEAPE COIMPANY, A. CORPORATION GENEVJ 012,151

I'EEANS FOR AND llilETI-IGD OF REDUCING CiztO S 'I'ALK IN FQUR-WIRECIRCUITS.

Application filed January 2, 1920. Serial No. 348,731.

To (all whom it may concern.

Be it known that I, RIorn-xnn A. RnnsHAw, residing at Woodhaven, in thecounty of Queens and State of New York, have in- 5 vented certainImprovements in Means for and Methods of Reducing Cross Talk in Four-l iire Circuits, of which the following is a specification.

This invention relates to transmission systems and more particularly totransmission systems of the type known as four-wire repeater systems.

The present application is related to a patent to O. B. Blackwell onMeans for and method. ct reducing cross-talk in tour wire circuits, No.1,394,062, October 18, i921.

In the said patent cross-talk interference between the circuits leadingin one direction and those leading in the opposite direction is avoid dby an electrical segregation of the conductors and repeaters of oppositedirections, this being accomplished in the embodiment of the inventiondescribed therein, by placin the repeaters of one direction remotelyIrom those of the other direction, and by providing four separate branchcables, one leading to the input sides ot the repeaters transmitting inone direction, another leading from the output sides of the saidrepeaters, and the other two similarly leading to the input and outputsides of the repeaters transmitting in the opposite direction.

In the present invention I propose to group together the conductorsleading to ti e input sides ot tie repeaters from both directions, andto group together also the conductors leading away from the output sideso'l'i all the repeaters, so that all the repeaters may be assembled inone group, without deleterious effect. conductors may be in separatecables or they may be in the same cable, one group being electricallyseparated from the other in any desired manner, for instance, in the waydescribed. in the above mentioned Blackwell application.

ii good understanding of the invention may now be had trom the followingdescription thereof, reference being had to the accompanying drawingshowing in diagrammatic view one specific form and arrangement oi?circuits embodying the invention.

In this drawing is shown a tour-wire transmission system extendingbetween stations A and C, through an intermediate repeater station B. Acable 10 extends from station A to station B and a similar cable extendsfrom station E to station 0. leach cable includes the conductors of aplurality of tour-wire transmission circuits. For purposes ofillustration three distinct rour wire transmlssion circuits are shown,but it will be understood that this number 15 merely illustrative andany desired humber of circuits may be provided. Each of the tour-wirecircuits terminates in twovire lines, such as lTW Ill/i and Iii/V atstatiop A. and. LE LE, and LE, at station (1. 'lhe lines Liv, and LE,are interconnected by means of a tourwvire circuit comprising thetwo-wire line sections W, and E, connected at the repeater station B bymeans of a one-way repeater R for transmission from west to east and theline section B, and W con nected by a repeater R at station E fortransmission from east to west. Threewinding transformers of the usualtype, Tit, and TE are provided to associate the conductors of thetour-wire sections with the two-wire lines, these transformers beingshown schematically in the drawing, it being readily understood that anyother suitable devices may be used for this purpose. The remaining twotour-wire circuits illustrated are similar in all respects to that justdiscussed and need .not be further described.

Currents flowing to the repeater stations from stations A and U areconsiderably attenuated when they reach the repeaters whereas thecurrents leaving the repeater station are comparatively strong. Unless,therefore, the conductors carrying the repeater output currents areelectrically separated itrom the repeater input currents, the saidoutput currents may cause cross-talk interference in the input circuits,of appreciable magnitude relative to the said weak input currents. Theelectrical separation between the input and output conductors isettected in the present invention by grouptogether the circuits leadingfrom stations A and C to the input sides of the repeaters, i. e., N N N11,, E and E, similarly grouping together the circuits leading from therepeaters to stations A and (l, i. e., E E E and W W and W andelectrically separating the two groups from each other. In the drawing Ihave shown the input conductors in one cable 12 and the outputconductors in another cable 13, but a like result may also be obtainedif the two groups are placed into one cable and shielded from each otherin the manner described in the above mentioned Bl'a'ickwell patent forexample. It will be observed that with this arrangement the eastboundand westbound repeaters need not be segregated from each other.Interference between the currents in the separate conductors of eachgroup may be kept within permissible limits bytransposition of theconductors, or by any of the other methods in common use. The manner inwhich cross-talk interference is prevented between the conductors incables l0 and 11 is described in the said Blackwell patent.

" Although I have herein shown and de- 'scribed only one form andarrangement of circuits embodying the invention, it is readilyunderstood that various changes and modifications may be made thereinwithin the scope of the following claims, without departing from thespirit and scope of the invention.

W hat I claim is:

1. The method of preventing interference between four wire circuits at arepeater installation, which consists in leading the wires carrying theweak input currents to the repeaters through one cable and leading thewires carrying the strong output currents away from the repeatersthrough another cable, the two groups of wires being electricallyseparated.

2. The method of preventing interference between the conductorscarrying, respectively, the weak and the strong currents at a repeaterinstallation, which consists in grouping together the conductors of bothdirections carrying the weak currents, similarly grouping the conductorsof both directions carrying the strong currents, and electricallyseparating the said groups.

3. The method of reducing the interference at a repeater station betweenconductors of tour wire circuits, which consists in groupingtogether theinput conductors of opposite directions, similarly grouping together theoutput conductors of opposite directions, and shielding the groups fromeach other.

4. In combination, a plurality of repeaters, four wire circuitsassociated therewith and comprising in each direction input and outputconductors, and a cablegrouping together the input conductors of bothdirections, :1. second cable grouping together the output conductors ofboth directions said cables comprisingmeans tor shielding the conductorsof one cable from those of the other cable.

5. In combination, a plurality of oneeway repeaters associated in agroup, tour-wire circuits associated with said repeaters, said circuitscomprising in each direction input tour-wire circuits associatedtherewith com-- prising a group of incoming and a group of outgoingconductors electrically separated and for a station in one direction anda group of incoming and a group of outgoing conductors electricallyseparated and for a station in another direction, a cable groupingtogether the incoming conductors from both directions and a cablerouping together the outgoing conductors 'l'rom both directions.

8. In combination a pluralit of repeaters, four-wire circuits associatedt erewith comprising a cable for a station in one direction'withincoming and. outgoing conductors therein electrically separated, acable for a station in another direction with incoming and outgoingconductors therein,

electrically separated, a cable grouping together the incon'iingconductors from both directions, and a cable groi lping together theoutgoing conductors from both directions.

In testimony whereof, I have signed my name to this specification this29th day of December, 1919.

RICHARD A, RENSHAW.

grouping together

